1. Field of the Invention
The present invention relates to a motor vehicle suspension having a rotary damper, and more particularly to a suspension suitable for use as a rear wheel suspension for a four-wheeled motor vehicle.
2. Description of the Relevant Art
One prior motor vehicle suspension having a rotary damper is known from Japanese Laid-Open Patent Publication No. 56(1981)-28008, for example. The disclosed motor vehicle suspension includes a casing fixed to the frame of a motorcycle and having a cylindrical oil chamber defined therein. The oil chamber accommodates therein a rotor angularly movable with a swing arm and having vane slidably held against the inner peripheral wall surface of the oil chamber.
Japanese Laid-Open Utility Model Publication No. 58(1983)-90810 discloses a rear wheel suspension for a motor vehicle. The suspension has a rotary damper including a hollow rotor through which a torsion bar extends. One end of the torsion bar is coupled to an arm integral with the hollow rotor. Alternatively, the damper case and rotor of a rotary damper are disposed in a hollow torsion tube, and the proximal end of an arm is attached to an outer peripheral surface of the torsion tube.
Generally, a suspension for a four-wheeled motor vehicle is disposed in a limited space within a tire housing, and is required to effectively dampen relative movement of the tire and the vehicle body. A suspension having a rotary damper is more advantageous than a conventional strut-type suspension in that it takes up a smaller installation space, i.e., it is a space saver.
With the conventional rotary dampers, however, the damper case is fixed to the motor vehicle body and the rotor and the vane are angularly moved with the arm. The rotary dampers are constructed of many components and complex in structure. Since the oil chamber is cylindrical in shape, the damper case is large in size and needs an extra space for installation.
Inasmuch as the arm is directly coupled to the torsion tube, vertical and fore-and-aft bending forces tend to be applied to the torsion tube through the arm. The area through which the arm is supported, i.e., the area through which the torsion tube and the arm are attached to each other, cannot be increased. Consequently, a reinforcing structure for the arm is complex.